It is known that in electrochemical cells which utilize phosphoric acid as the electrolyte there is some evaporation of the electrolyte into the reactant gas streams as they pass therethrough, particularly into the air (oxidant) stream which flows at a significantly greater rate than the hydrogen (fuel) stream. Although this evaporation is slight, it becomes significant over a long period of time and may eventually result in failure of the cell due to an insufficient quantity of electrolyte remaining within the cell. The problem becomes more severe as cell operating temperatures increase. Therefore, for extended periods of operation it may be required that this evaporated electrolyte either be replenished intermittently or continuously from a separate source, or the lost electrolyte must be recovered and returned to the cell. Even if electrolyte loss is sufficiently slow such that it would not have to be replaced during the design life of the cell, the phosphoric acid which leaves the cell in the reactant gas stream is highly corrosive and is preferably removed from the cell exhaust products before it does damage to components downstream of the cell. No commercially suitable solution to electrolyte evaporation problems has yet to be devised.